From: Rick DeNatale <rick.denatale@...>
Date: 2007-10-15T03:28:25+09:00
Subject: Re: Parameter in a block is not local?

On 10/14/07, SpringFlowers AutumnMoon <summercoolness@gmail.com> wrote:
> I thought a iterator with a block is like an nameless function call...

Similar, but not the same.  Blocks are closures, so for example:

a = 1
1.times {p a}

will print 1 since a in the block refers to a in the outer scope.


> so if it is a function call, the parameter is local.
> but for the following, the output is surprising:
>
> a = 1
> p a
>
> 1.upto(10) {|a| p a}
>
> p a
>
> --------------
>
> E:\>ruby test_iterator.rb
> 1
> 1
> 2
> 3
> 4
> 5
> 6
> 7
> 8
> 9
> 10
> 10
>
> a is changed!
>
> but is it true that the "a" is not global to begin with....
> but then, isn't the "a" inside the block more local than the "a"
> outside?

In Ruby 1.8 a block argument acts like a local in the containing scope.

This is changing in 1.9

http://eigenclass.org/hiki/Changes+in+Ruby+1.9#l8


-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/